High airtightness and high thermal insulation of residential houses have been required in recent years due to energy-saving consciousness, obligation to comply with the next-generation energy saving standard and the like. With such enhancement in heat insulation performance of residential houses, it is expected that the necessary thickness of thermal-insulating materials is increased. Because of oppression to the interior living space and the limited space inside wall bodies, a problem of necessity for changes in the design due to addition of thermal-insulating materials has been caused. The thermal-insulating material is constructed inside the wall body, and thus, its replacement during habitation is very difficult. Accordingly, it is required that the thermal insulation performance be maintained for a long period.
As thermal-insulating materials for residential house applications, fiber thermal-insulating materials, such as glass wool and rock wool or foamed plastic thermal-insulating materials formed by foaming styrene, urethane, or phenol resins are used. Of these, as for the foamed plastic thermal-insulating material, it is known that its thermal insulation performance is greatly influenced by the type and condition of a foaming agent included in its cells.
Chlorofluorocarbons (CFCs), of which the gas thermal conductivity is low, had been conventionally used as a foaming agent for foamed plastic thermal-insulating materials, but abolition of the use of CFCs was specified by the Montreal Protocol, adopted in 1987, because CFCs are significantly responsible for destruction of the ozone layer and climate change. As a result, a shift of the foaming agent to hydrofluorocarbons (HFCs), of which the ozone depletion coefficient and the global warming coefficient are relatively low as a foaming agent, has progressed. However, since HFCs still have a high global warming coefficient, a shift to hydrocarbon foaming agents has been required.
The hydrocarbon foaming agents, of which the ozone depletion coefficient and the global warming coefficient are very low, are highly excellent foaming agents from the viewpoint of environmental destruction. Meanwhile, there is an issue of their higher thermal conductivity and flammability, compared to the conventional chlorofluorocarbon foaming agents, and a solution to the issue is required.
In Patent Literature 1 and Patent Literature 2, a large number of gas species are disclosed as halogenated hydroolefins, of which the ozone depletion coefficient is zero and of which the global warming coefficient is low.